Why are GPS units showing up everywhere? You might find one in your rental car, on your wristwatch or even built into your wireless phone. Anti-theft systems use one, heavy construction equipment might use one and having one on your boat now seems to be a requirement. Anytime we want to know our exact location on the face of the Earth, the GPS becomes indispensable. Like many other technologies, feature rich GPS units are now affordable for the average person. So how do you know which one to purchase? Let's look at few things to consider prior to buying your next GPS unit, but first, what is a GPS unit?

A GPS (Global Positioning System) unit has the primary function of calculating its own location on land or water by using satellite signals. Once the GPS unit knows its own location, it can help the user determine direction and distance to other known locations. For instance, a GPS on a boat can tell the captain how far it is to the shoreline or how far it is to a favorite fishing spot. For the outdoor sportsman a GPS can help with finding your campsite, your vehicle or your next geocache. Popular outdoor activities such as hiking, hunting, fishing, trail running, backpacking, rock climbing, canyoneering and canoeing are all made more enjoyable and safer when you take along your GPS.

When buying a GPS system the first thing to consider is how you intend to use it. If you plan on using it while on foot, you'll want a GPS that is lightweight, compact, weather resistant and that is equipped with features important to foot travel. WAAS (Wide Area Augmentation System) is one such feature. WAAS greatly increases the accuracy of your GPS, in most cases to within 10 feet. Accuracy within a few meters is important for the outdoor enthusiast but not nearly as important for navigating through town in your rental car. Next, be sure your GPS has at least 12 channels of reception too. Since your GPS will only work when it receives signals from satellites orbiting the Earth, less than 12 receiving channels will not get the job done in wooded areas or in steep terrain. If you plan on using your GPS to navigate while driving in your car, its weight is not nearly as important as its ability to display street maps. The GPS mounted to the dash of your truck probably doesn't need to be weatherproof, but the one on your boat better be.

Here are the features and products I recommend. For the outdoor athlete or sportsman, be sure your GPS has these features: topographical mapping, back tracking, a computer interface, weatherproofing, 12 receiver channels and WAAS. I recommend portable GPS units in the Garmin eTrex Series and the Magellan Meridian Series. For driving applications, be sure your GPS has these features: street mapping, large display, a computer interface and external antenna compatibility. I recommend automotive GPS units in the Garmin StreetPilot Series and the Magellan RoadMate Series. For boating and other marine applications, be sure your GPS has these features: marine mapping, color screen, active sonar, back tracking, a computer interface and weatherproofing. I recommend marine GPS Units in the Garmin GPSMAP Series.

Prices for GPS units vary a great deal and in general, you get what you pay for. While some units cost around $100 and offer relatively few features, others may cost as much as $1000 or even more and are loaded with dozens of features. Here is a good rule of thumb for determining how much money to spend on your next GPS. You should expect to pay between $200 and $300 to get a decent GPS Unit. I own a Garmin eTrex Vista. I believe it is the best GPS available for under $300.

If you don't have a GPS or yours is more than five years old, now's the time to get one. Adding a new GPS to your inventory of backcountry toys will take your outdoor adventures to a new level of enjoyment. Use this information and you'll Get It Right The First Time. Get Outdoors!

Chuck Fitzgerald is the owner of Arizona based BackCountry Toys, an online specialty store with the "Best Gear Out There" and dedicated to helping outdoor enthusiasts to "Get It Right The First Time" with timely educational information. Please visit http://www.BackCountryToys.com/ to find great gear and to receive the Fact & Tips e-newsletter, "FreshAir." (800) 316-9055.